PPI Calculator
Calculate a screen's pixel density (PPI) from its resolution and diagonal size.
About the PPI Calculator
Enter the screen's resolution and its diagonal in inches. The calculator gives pixels per inch, the dot pitch, the physical width and height, and the total megapixels.
Pixels per inch is the diagonal resolution in pixels (√(width² + height²)) divided by the diagonal in inches. At typical viewing distances, about 90–110 PPI suits desktop monitors at 100% scaling, while phones exceed 400 PPI because they're held closer.
The formula
PPI = √(w² + h²) ÷ diagonal
Worked example
A 27-inch 2560 × 1440 monitor
- Diagonal in pixels: √(2560² + 1440²) = 2,937
- PPI = 2,937 ÷ 27 = 108.8
- Dot pitch 0.2335 mm; 3.69 megapixels
Questions people ask
PPI vs DPI?
PPI is for screens; DPI is printer dots per inch.
What PPI looks sharp?
Depends on distance: about 300 PPI at 30 cm, 110 PPI at 70 cm.
Is a 27-inch 4K monitor sharper?
Yes: 3840 × 2160 at 27 inches is about 163 PPI, usually used at 150% scaling.